[#482] reputation/router: Move router to ./common

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

pkg/services/reputation/common/router/util.go

@@ -0,0 +1,39 @@
+package router
+
+import (
+	"bytes"
+	"errors"
+
+	"github.com/nspcc-dev/neofs-node/pkg/services/reputation"
+)
+
+var errWrongRoute = errors.New("wrong route")
+
+// CheckRoute checks if the route is a route correctly constructed by the builder for value a.
+//
+// Returns nil if route is correct, otherwise an error clarifying the inconsistency.
+func CheckRoute(builder Builder, epoch uint64, t reputation.Trust, route []ServerInfo) error {
+	for i := 1; i < len(route); i++ {
+		servers, err := builder.NextStage(epoch, t, route[:i])
+		if err != nil {
+			return err
+		} else if len(servers) == 0 {
+			break
+		}
+
+		found := false
+
+		for j := range servers {
+			if bytes.Equal(servers[j].PublicKey(), route[i].PublicKey()) {
+				found = true
+				break
+			}
+		}
+
+		if !found {
+			return errWrongRoute
+		}
+	}
+
+	return nil
+}